New Democratic Party Leader Thomas Mulcair has essentially adopted the Obama doctrine when it comes to approving new oil sands pipelines – projects would be judged based on whether they significantly increase Canada’s greenhouse gas emissions.

The NDP’s policy is not to shut down the oil sands – or even to rule out some expansion of production. But the party is promising a national cap-and-trade program aimed at meeting Canada’s international obligations on reducing greenhouse gas (GHG) emissions, and Mr. Mulcair said an NDP government would toughen environmental reviews for pipeline projects to ensure they are consistent with those obligations.

In essence, Mr. Mulcair is mimicking U.S. President Barack Obama’s stand on the Keystone XL pipeline, which the President has said he will only approve if it does not add significantly to carbon emissions. Under the NDP version, “does not add significantly to emissions” would be replaced with “is consistent with Canada’s climate targets.”

The obvious question is: what do those targets mean for key sectors of the economy, including the oil sands? It’s a question that neither Conservative Leader Stephen Harper – who set the targets – nor Liberal Leader Justin Trudeau – who says a credible climate policy would facilitate oil sands growth – nor Mr. Mulcair himself has answered.

“What we’re talking about here essentially is a no-growth scenario [for the oil sands]; we’re not talking about total phase-out in the near term,” Louise Comeau, executive director for Climate Action Network Canada, said Tuesday. She said reducing emissions in the oil sands is an important part of the solution. But the key is to reduce oil’s dominance in car and truck transportation, and to speed up the phase-out of coal from electricity sectors in provinces such as Alberta, Saskatchewan and Nova Scotia.

At the United Nations climate summit in Copenhagen in 2009, Mr. Harper committed Canada to reducing GHGs by 17 per cent below 2005 levels by 2020. And in the runup to the Paris summit this December, he went further, telling the UN in May that Canada would reduce emissions by 30 per cent from 2005 levels by 2030. But the Conservative government has offered no plan to meet either the 2020 or 2030 commitments.

NDP star candidate Linda McQuaig recently provoked controversy – and attacks by both the Conservatives and Liberals – when she suggested that “a lot of the oil sands may have to stay in the ground” if Canada is going to meet those targets. Despite the uproar, Ms. McQuaig’s comment was hardly radical. With 168 billion barrels of reserves, industry could double production to five million barrels a day for 50 years – and still have lots left in the ground.

Environmentalists say Ms. McQuaig was merely reflecting Environment Canada’s own analysis – and the reality of the country’s challenge – by suggesting that brakes will have to be applied on oil sands development.

Environment Canada forecast last year that, under current policies, emissions from oil sands would grow by 45 million tonnes between 2005 and 2020, and that the country would miss its 2020 target by 116 million tonnes. If that’s the case, Canada would have to reduce emissions by 171 million tonnes a year between 2020 and 2030.

Lower oil prices – if they persist – would reduce that oil sands growth forecast. After a year of slumping oil prices, the Canadian Association of Petroleum Producers cut its forecast of oil production in 2030 by more than one million barrels a day – though it would still be 1.7 million barrels a day higher than it is currently.

The NDP says it will assess pipeline proposals to ensure they’re consistent with Canada’s emission-reduction goals, but is vague on whether those goals can accommodate rising oil sands production. A lengthy bout of low oil prices could achieve more than any government policy to rein in industry emissions.